Thesis defense of James Andrew Gooding

Trigger systems of high energy physics experiments are crucial to the processing of the immense quantities of data produced from particle collisions. The Large Hadron Collider beauty (LHCb) experiment underwent a major upgrade between Runs 2 and 3 of the Large Hadron Collider (LHC), in which the trigger system was redeveloped from a hardware-and software-based model to an entirely software-based model. This thesis presents measurements with proton-proton collision data recorded by the LHCb experiment for both of these models, and the commissioning of the software-based trigger.

The first ever measurement of the time-integrated untagged charge-parity (CP) asymmetry in the decay of Bs0 -> Ds-Pi+, is presented, performed with of 5.7 fb-1 of data recorded in 2016-18. An ongoing measurement of the lepton flavour universality ratio in B+ -> J/psi(l+l-)K+ decays, rJ/psi, using 4.5 fb-1 of data recorded in 2024 is then presented. This measurement validates the techniques used to evaluate efficiencies and data-simulation differences on these newest datasets, ahead of analyses in the rare B+ -> K+l+l- decay modes. The impact of removing the hardware trigger is discussed throughout the thesis; the realisation of the anticipated improvements in trigger efficiencies is demonstrated explicitly.